Hydraulic brake master cylinder



llg- 14, l95l N: E. WAHLBERG l 2,564,137

HYDRAULIC BRAKE MASTER CYLINDER Filed Feb. l2, 1945 2 Sheets-Sheet 2 ww f M//Z INVENTOR.

g' I f y 4/ f/ sa 282 284 256238 228 ,WwW/Hf fPatented Aug. 14, 1951 HYDRAULIC BRAKE. MASTER CYLINDER Nils Erik Wahlberg, Chicago, Ill., assigner to N ash-Kelvinator Corporation, Kenosha, Wis., a

#corporation of Maryland Application February 12, 1945, Serial No. 577,474

18 Claims.

This invention relates to hydraulic brakes an more particularly to a master cylinder for a hydraulic braking system for automotive vehicles.

It is an object of this invention to provide a brake master cylinder which is easy to manufacture, is of relatively cheap construction and yet which will perform its assigned function efciently and in a dependable manner.

It is afurther object of the invention to provide a master cylinder which can be assembled from parts which are simple and cheaply made.

It is a further object of the invention to overcome the defect of porosity in a master cylinder, to which most master cylinder castings are subject.

It is afurther object of the invention to provide a master cylinder in which the advantages of cheapness and efficiency are present, which will function to maintain pressure in the fluid lines of the system while the system is not in use and yet which will function to bleed air and vapor bubbles from the system as well as to illl the system upon each actuation of the brake pedal without the necessity for employing the usual flow retarding and pressure maintaining Valves such as are common in master cylinders today.

Further objects and advantages of the invention will appear hereinafter as the description proceeds and will be pointed out more fully in` connection with the appended claims.

In the drawings, of which there are two sheets:

Figure 1 is a diagrammatic side elevational view partially in section of a brake system showing the master cylinder and actuating means of the present invention;

Figure 2 is an enlarged side elevational view of the master cylinder in partial cross section in orderI more clearly to illustrate the same,'the master cylinder piston being shown in its normal at rest position;

Figure 3 is an elevational View, partially in section, of a modification of the master cylinder and actuating mechanism shown in Figures 2 and but showing the piston in its retracted position as the brake pedal nears the end of its retractile stroke; f

Figure 4 is a plan view, partially in section of the actuating means shown in Figure 3 taken upon a plane as indicated by the line 4 4 of Figure 3 and looking in the direction of the arrows;

Figure 5 is a plan view, partially in section of the actuating means shown fin Figure 2 taken upon a plane as indicated by the line 5-5 of Figure 2 and looking in the'direction of the arrows;V

Figure 6 is a view similar to Figure 3 showing a modified form of the invention;

Figure 7 is a sectional view similar to Figure 6 but showing the brake actuating means and pist0n in its normal at rest position and in this respeci; similar to Figure 2;

Figure 8 is a view similar to Figure 7 but showing the master cylinder with the piston and brake actuating means in the fully applied position;

Figure 9 is a partial side elevation of a brake actuating means illustrating a further modification of the same and showing the actuating mechanism in a position similar to that shown in Figures 3 and 6;

Figure 10 is a side elevation of the mechanism shown in Figure 9 but showing the brake in fully applied position;

Figure 11 is a side elevational view of the mechanism shown in Figures 9 and 10 but showing the actuating mechanism in the released or at rest position of the master cylinder; and

Figure 12 is a horizontal sectional View of the mechanism shown in Figures 9, 10 and 1l through the brake actuated mechanism taken substantially upon a plane as indicated by the line l2-I 2 of Figure 1l and looking in the direction of the arrows.

Referring in detail to the drawings, in which similar reference characters are employed to designate similar parts, the system is illustrated in Figure l as comprising a set of brake drums l Which may be suitably mounted upon wheels of a vehicle (not shown), the brake drums being provided with backing plates l2 supported from the vehicle and in turn supporting, by any desired means, brake shoes i4 provided with friction facing material I6. The brake shoes Id are, in this case, of an internally expanding variety and are adapted to be urged into braking position against the interior of the drums l2 by means of motors comprising wheel cylinders i 8 located between adjacent ends of the shoes iii for spreading such ends apart and forcing the friction surfaces I6 into contact with the inside diameter of the drum l0.

The wheel cylinders I3 are actuated by means 0I the uid lines 29 which are supplied with iluid under pressure through a coupling 22 from the brake master cylinder illustrated in general at 24. The coupling 22 may be provided with a male thread threadedly engaged with the female pipe thread 26 (see Figures 2 and 3) provided in a plug 28 threaded into the end of the master cylinder as will be more fully explained later.

The master cylinder proper comprises a body 39 which may be cast of iron or any other suitable material. It should be noted that the body casting Sil is of single wall thickness and therefore can be manufactured quite simply without the necessity for using multiple cores and may inm deed be made from a green sand core with only a single internal core. Thus the danger of porosity is avoided by not having a core within a core in the casting process. The body casting 35 is provide-d with a pair of aligned apertures 32 and 34 in opposite longitudinal ends thereof. Such apertures may be cored in the casting but in any event are later drilled and reamed to size to provide perfectly aligned 4seats in which a seamless tube 36, which may becenterless ground to proper size, is inserted. The tube may have a pressed rit with the inside diameterrof the. apertures .'52 and 34 and is 'also internally breached for final finish prior to assembly` `with the body Sil.

The final assembly. v of the` tube to thebody is made by threading thepipe plugsr and into the endslof'fthe tubeQfThe threaded ends of pipe plugs .28 and 38' being tapered will expand the endsfo'fth'e tube ilintofluid-tight Contact with the walls of lthe apertures 32 and de. it should be noted that while the plugs and 38 are described` ashavingfpipe threads, these threads are actually full threads arranged upon a taper so that there is aY complete engagen ment of threads throughout the entire lengthof the surfaces in. contactfanclmarenot identicalY with pipe threads exceptwthatthe ge'nera'lconl Y tour is tapered.

'irior to threading therfront; plug 38 into its respective end oft'ubed,` thepi'ston t and co-1 operating mechanismds inserted through said end into tube 3S to complete the master cyiina der. The pistonfli vis'"provided upon its rearu wardly presented. surface with a cup washer d2 of rubber or similariieirible elastic material, such cup washer Ahaving a disc-dike body portion i4 and a peripheral, upstanding, tapering flange E extending'circumferentially thereabout and acting to seal the cupw'aSher :l2 against the inside walls`l8 of the cylinder 3E.

The piston di! is providedwith a blind hole Sii extending from its front surfacetoward its rear surface, the bottomof s'u'ychhole being provided with a partially spherical'depression within which there is received the. ballend 5ft of a rod et. 'nieren end 551er me is heid in piace upon the partially spherical seatu by means of a sleeve nut 5d threadedly received within the hole 59 and having a rear surfacev (see 'Figure 3) shaped toy fit the forward surface of ball rEhe piston/is also provided with a pe ripheral groove 62 within which there is receiv l a sealing member Ell having an inwardly extend ing annular flange 6 seated in the innermost portion t8 of groove G2 and a rearwardly extend-l ing annular lip which coacts with the i ternal cylinder wall 48 to providean atmospheric seal against the loss of `fluid forwardly of the piston.

The wall of cylinder is provided with "a port 'i2 which opensinto the reservoir provided by the master cylinder body .3J for the purpose of lubricating the piston in its motion along the internal cylinder wall it and with a series of small ports i4 which are arranged with their axes in the same vertical transverse plane of the cylinder and slightly behind the fully retracted position of the piston cupv washer lip when the piston is in its fully retracted position. Ports ifi provide means for initial lling and constant in the opposite direction.

replenishment of the cylinder and system and for the bleeding or elimination of air and vapor bubbles which may collect within the system.

t will be understood by those skilled in the art that piston le will of necessity be of a slightly smaller diameter than the inside walls i8 of cylinder 35 so that said piston may be freely reciprocable` within the Vcylinder. 4PistonAl is provided with a fluid seal Gil near its retractile side which is of a type to prevent any fluid flow in that direction. Cup washer lid is positioned against the opposite end of piston tif! and is of such a design that fluid may oy-pass cup washer fifi to the compressive side of piston (lo but not Port '52 formed in cylinder 3e is provided to lubricate piston de by permitting fluid from the reservoir to contact said piston. Further, said iiuid will flow through port l2 and fill the space between the outer surface of piston lil and the inner' `walls of cylinder 3E and will be drawn past cup washer.44 if a.A vacuum is created on the compressive sidev Y.of-H piston 4G. Such a vacuum will only be created when there is a lossof fluid from the, YSystem which is undesirable and abnormal. ,e If lsuena loss is so small as not to be or" a serious nature.` the small amount of fluid which can bypass cup washer d will compensate fornthis sloslsk, If the loss is greater, it will be found thatfsome,

thing is radically wrong somewhere in the braise L* system and provision for supplying a vgreater amount of uid lay-passing eupwasherd would.;

not remedy the defect; in this v2ase,thewhole.;-l

system must ce checked and the defect repaired;` Y

The cup washer 42 may be heldin placeupon the rear face of the piston 4U by means oi-a compression cup Washerlspring 16 havingoneend .1KA

seated upon the innermost face ofthe plug 28. and its other end seated in a retainer i8 which rests upon the exposed surface of the cupiwasher.

Spring i5 constrains the cupgwasher to ,fol-,H low the piston in its movements. The piston will be urged in the retractile strolredirection .by the spring 'i3 but this retractile force is counter-.-

balanced by a short and somewhatheaver com.-

pression pressure-maintaining Aspring 8G, which,

has one end seated upon the-front end ofzthe sleeve nut and its other end seated upon a surface of a washer 82 which visgheld in place Within the cylinder36 by means of* thervplug 3S.; The pressure-maintaining springA Sil being` stronger than the cup washer springfi tends .to. force the piston rearwardly against the retract-` Y ing action of the spring 16 and normally has soffre, cient force to move the pistonA ,rearwardly/,to such a position that the lipd ofthe cupgwasher l2 overlies the series of apertures .fili and thus,

produces a slight fluid pressurein the system..

The forward end of the rod 56 terminatesiln the modification shown in Figures and .4) in a threaded end which may be threadedvintoran .L shaped forging s4, a lock nut 85 beingernployed for holding the rod against retractionfrom its,

threaded engagement with lthe forging 84. .Y The, forging S4 has a front portion 8B whiclrformsthe foot of the L. The forging ,B4 is also provided. with a slot within which a pin 92 is slidable for a purpose which will be later explained..

The pin 92 is pivotally receivedwithin an aper-l ture 94 formed in a second L-shaped forging 9S. and having a forward end 98 provided withal curvature Illu concentric to the pin. 92.;Y The foot 88 of the L-shaped forging 84 has a curvature l B2 mating with the curvature |00 of the release. member 96. The rearward end 104 of the release A member 96 extends laterally and upwardly and is tapped to receive a stud IIlB which is adjustably locked in place by means of a lock nut |08. The stud |66 is adapted to abut against the underside of a pedal lever arm III! so as to cause a release of the curved surfaces I() and |62 from one another as the pedal II2 nears its retracted position.

The pedal II2 is mounted for rotation upon a shaft II4 extending transversely of the vehicle and is urged to its uppermost position by means of a spring II6 which is coiled around the shaft II4 having one end IIB inserted in a hole in the shaft I I4 and its opposite end provided with a hook I2Il exerting a force against the pedal I I2 tending to rotate it in a clockwise direction as viewed in Figures 1 and 3 about the shaft I I4.

'Upon depression of the pedal II2 resulting in counterclockwise rotation thereof about shaft II4, the first action of the mechanism results in movement of the pin 92 to the rearward end of the slot 90 of the forging 84 to take up the lost motion. A coil spring I 22 having one end anchored in a lug I24 upon the pedal lever II2 and its other end anchored upon an extension |26 from the release member 96 tends to rotate the release member 96 in a counterclockwise direction around pin 92 as viewed in Figure 3 to cause the curved surface IIlIl to drop down within the curved surface |02 as the pedal proceeds toward brake-applied position. While this is occurring, the slack existing between the slot 60 and pin 92 has been taken up and the piston Il@ is moved from its at-rest position to compress the fluid to the rear thereof and force fiuid into the system in quantities sufficient to actuate the wheel cylinders I8.

When the brake pedal II2 is released, spring II6 tends rapidly to return said pedal to its retractile position, thereby retracting the rod 56 and piston 4U and causing the cup washer 42 to follow the piston under the impetus of cup washer spring 76. In its retraction, the piston 46 is forced to return to a position shown in Figure 8 with cup washer @2 forward of the ports 14, thereby exposing them to the fluid reservoirV Y existing within the master cylinder body 36 and permitting any air bubbles or vapor bubbles trapped within the cylinder to escape by means of the ports 'I4 and the place of said air or vapor bubbles to be taken by fresh uid from the reservoir through the lower ports 14.

As the pedal I l2 approaches its fully retracted position, the stud IlI upon release element 96 being in contact with the arm Il of the brake pedal lever II2 will cause the front end I0!) of the release element 66 to lift out of contact with the curved surface Ill2 of the L-shaped forging 84, permitting said L-shaped forging 84 and the piston rod 56 to be returned to the position shown in Figure 2 under the impetus of pressure-maintaining spring BIJ.

In order to fill the system at the time that it is installed, it is only necessary to open bleed valves at the wheel cylinders and to pump the brake pedal back and forth, permitting it to release at the end of each stroke as described above. 'I'his will cause rapid flow of uid throughout the system by reason of the intake upon each stroke of quantities of fluid through the ports 'I4 and the exhaust of air at the bleed valves of the wheels.

The position occupied by the cup washer 42 in the normal at-rest condition of the braking system as shown in Figure 2 operates effectively to impose a spring produced pressure upon the fluid" in the system. The cup washer spring 'I6 is not strong enough to counterbalance pressure-maintaining spring 86 but cup washer spring 'I6 plus the residual pressure in the system will effectively balance the pressure-maintaining spring 8U to insure an at-rest position corresponding approximately to that shown in Figure 2. -The relative strengths of the springs 16 and 66 are such as to create a residual pressure within the system of approximately ve to ten pounds per square inch and this pressure effectively prevents the entrance into the system'of air, dirt and other foreign matter by the expansion of the cup washers both at the wheel cylinders and at the master cylinder against the cylinder walls. v

Referring briefly to Figure 5, the mechanism therein illustrated is an equivalent form of release mechanism to that shown in Figures 1 to 4 and comprises a forging l5!) into which the piston rod 56 may be threaded and secured by a lock nut 86. Forging |50 is provided with a rectangular slot |52 in its forward end within which a release member |54 may be received for pivotal movement upon a pin I56. Pin |56 is adapted to be rotatably supported upon the lower end III) of the brake lever and is `slidably received within slots I58'forrned in opposite sides of the rectangular portion of the element |56. The front portion |60. of the release element I54 and the rearwardly directed front surface I62 of the forging I 50 are .designed to cooperate with one another in the same manner as the surfaces i60 and |62 of Figure 3. vided with a Stud |64 similar to stud I 66 of Figure 3 and a spring (not shown) may have its lower end anchored in the lug I66 similar to |26 of Figure 3 and upon the brake .pedal lever for the same purpose as shown and described in connection with Figure 3.

In Figures 6, 7 and 8,a slightly different form of the invention is shown. In this instance the body or reservoir 232 is formed of a single casting together with the cylinder 236 and the ends of the cylinder are faced off to provide seats for gaskets 221 and 237. The plugs 228 and 238 closing the ends of the cylinder 236 are provided with annular flanges 229 and 232 which seat upon the gaskets 221 and 23?.

In this modification, the piston 242 is shown as having the cup washer 242. attached thereto by means of a stud and lock nut 253 and the piston rod 256 is shown as being integral with the piston 240, the forward plug 233 being provided with an aperture for slidably receiving and guiding the piston rod 255 to retain it in a position for straight line motion. A pressure-maintaining spring 280 may be interposed between the plug 238 and the piston 22e for returning the piston to the nal at-rest position as shown in Figure 7. This pressure-maintaining spring 286 is of suicient strength to impose a prede-.ermined pressure upon the fluid remaining in the system of approximately five to ten pounds per square inch when the cup washer 242 and piston 249 have moved into the position shown in Figure 7 and when such pressure has been built up, the pressure-maintaining spring 286 and pressure retain the piston 246 in a position ef balance, closing oil ports 274 as shown in Figure 7.

The release of the piston after it-has been retracted to the position shown in Figure 6 is ac complished by the arrangement of a cam 262 upon the lower end of the brakepedal SIB. The cam 282 is provided vwith a portion 284 of uniform Therelease member |54 is also proamante-m;

diameterto operate. againstthe rearwardend- 2.86155 ofi-a slot288 formed-in the frontportion of-the piston =rod 1256:- .1. Cam.282fis also..zprovided.with a lobe 290 havingl sha-rp cutoff portionze :as *willN4 shortly `.be explained. .-1 To'. begin theA compression; 55 strokeiv the .carri 282fnioves; fromthepositioni shown'inFigure 7 first'ftottakeifsup .thefslaclr ex-A` isting. between surface. 284.9.nd-surface'286; :When 1 this lost motion has.beer1;..talienV upirthe.. pedale 3 l 0 Vfunctions directly 1through;.contact betweenlo surfaces V28d and 286 .torzurgefgzthe piston rodg andv .piston 2do rearwardly to produce pressure. withinthe cylinderfZZ-l. for distributioni through; u the fluidY lines .to the Wheelcylindersv With .the brakezgpedalfully` depressed; the pis? :f l 5 ton 24o .lies in' thev positiorrrshownf in Figureigi andit will benotedz-.that-zthe 1obe129 invsueh instance lies 4Wholly within.the slot .2 88 `with ther.; surface. of the lobe ,2% abutting'-,against;.1;the rearwardly presentedrsurface#291of theisloV Upon release of rhe'bra1;e.pedal,ta returnpspring- (similarfto that shown;in1Figure13) tends to re-` turnthe-pedal to its normal position and lobeieilvz. drivesy .the lsurfaceV 29| toward the` front; of the. vehicle toretractfthe:pistonrod 256 andzpston Upon. reaching Y*the position Shown in Figure 6., the. lobe .290 moves .out ofngagementwiththe g surface. 253i; thereuponf releasing. the `pistonirod- :fromv the influenceof 7the camp-lobe 2do and peri 30 mittingthe. compressionfmaintaining .spring 230v tdurge the pistontoward theright asyiewediin Figuref l'7 for the-flpurpose V.of compressing 'the- Y fluid inthe system to .thezdesiredresidual presn` sure. While the lobe :290 is retractingl the ,piston .35 240 and cup Washer 242 beyondthe port 21d, the air:v and vapor. bubbles, .if any. have collected .withi in` theV master cylindenfgare.released; and re1- placed by iluid lowing..into.;the master cylindera; through the lower ports. Again, in .this instancazflo pumpingv of fluid into the :system `is accomplished by; moving the brake. .pedal fbackand forth and g, permitting it to releaseatlthe-endof eaclrstroiie;A -H- as:,.explained in connection@with Figuresgl tod, inclusive.

Referring to Figures 9 $10,. 11,and.12, there fis a illustrated a still. further.Y modifications-of they. release mechanism :to insure iulLretractile. move ment of the piston prior to theigsystenrcoming.: to f rest.. ln this instance,the-.piston `rod- 356 .is 50 receivedwithinan aperture in a stamping 35B and held inplace means o f nuts 360' threaded upenn-2. the piston rodA 355 upon oppositegsides of the .g stamping 358. The Vstamping-is of jgeneral .box- 1. shape and has a closed/forward. end;.362. .-Opi-f-55 posite Ysides of the stamping Aareprovided with.; slots 36S within whiohya pin 386 is slidably re-- ceived, pin 365 being pivotally'retained within` the o. lower end of a brake pedal.;368; Als.o-.pii fotedupon the pin 356 is ai release. stamping which ..60

is roughly triangular ingvertical side.elevation-lv and 4which is formed'of stamped metalgto provide a box'section in vertical; :elevation Wththeforft ward ends of the box welded together to .provide if.:- a spring seat V3`l2 and 'La camsurface Sie for cof-.;65 action with a cam surface Bildformed uponxthe;1` outerstamping 358.

The rearrnost surface. of the; release stamping.: 3io-,has V.threadedV thereintoga stud I318 held in adjusted position byf'a locknut 38o, :such stud 70 being employedto contact 1an abutmentglas shown Vi-n- Figures f9, 10 andrll upon; the.: lower t: end -of the lever '368 gtopiovidegfor. 'svi/inging. they. stamping 310 ina clookwisedirection about the pirrin oppositiongto :the Iorce .exerted-by a 75 spring .drhaving itstoppositerends; anchored-f; upon'. a .land .386 .iformedsonrleverf S .and the springseat32 uponfstamping 3io. As .the stamping; is .rotated clockwiseoutof its position... as.. shown.. in Figure l0., .earn surfaces. 3M and Siiare moved.soutsofffengagement.. with. one anotheny thelpressurefmaintaining. spring urging. the piston to its normal position takes effect .and causes overlapping of vtheparts 3io and .upon one .another..=as.sho.wn in Fgurell .andto the..5. extent. permittedxby the'y surfaces. Sliand sie.; Surface YSiiljn suenan instance..functionszasga stop: .element to prevent-.undue vprojectionof the pistonawithin the cylinder and'. as. an. additional. safety .feature to prevent the .residual g pressure. from :becoming .too large.: I-ioweverg.V under Lnor-:.1 mal circumstancesvpthe rateyof the'sprng;;.;or;. urging Vthe ypiston rearwardly'.` is .sochosen .asato diminish quite rapidly. once the; cup `washer :has passed 4.the f ports :giving the master,..cylinder;ac. cess to vthe reservoir andiyet with :adequate pro-.1 3 vision beinggmade for maintaining. a minimum.; residual pressure i within the system.A

It will thus be seen'thatrneansfhave been pro.y vided forV building-a brakecmaster cylindertin.. whichthe brake mastericylinderzis so connected i. to a brake pedal andztothel remainderpi a fluidy. braking systernthata residualpressureiis main-: V tainedln the systemfatalltimes to preventleak ing loi yfluid out of the system and to prevent the; leakage-oran into the system.; rEhe system is ,Y also so constructed. as to'fpermitv thefescape cfg air Pandfvapor bubbles.;.from.t.the Vsystem and. tot... permit the llingnof voidszin the system caused x by' such.` bubbles'v upon-.1each;..actuation .of' `the brakesfv It willsalsobeznoted that thesystern-.is 1. simple to construct and readily lends itsel to present lday;manufacturingprocesses Whilejthe inventionihasbeen-described incon: i f siderable detail, isuehcdescriptiongis Anot to 1 be.M taken. as limitinggthejnvention All equivalents falling within;the:scope `of *..the vattached claims 1 are., expressly reservedc i'.

Wlratis claimedris:

l. In a fluid pressure system, a reservoir, iiuidy; insaid'reservoir, a cylinder supportedainsaid reservoir in .a horizontal -positionz andysurrounded; bysaid .fluidyga pistominsaidcylinder -recipro-:z Y cable. from la fully.retractedgpositionto a fully ".extended? position; fmeansgfor reciprocating said pistoma plurality of ports extending-,throughthe wall of said cylinder andzhaiing; theirprincipal axes located-in.the .samevertical transverse plane of thegcylinderrandi spring meanssurgingfsaid u '.pistonfto ra position of rest-in uwhich said piston overlies and;.closes-said ports; said piston-reclproeatingV rrleans;` including a onefwayA releasable drivingziconnection for gretrfacting; said piston; to i its-fullyretractedpositioni-toclear sai-d` ports; said connection being.; broken 1 upon the piston. reaehinglitsfully 'retracted :position:

2. In a fluid pressure system; a cylinder.,v `a pedal let/ ergapistonayithin said cy ier, a piston rod'iconnecting-said:pistoniwith the pedal lever, a slot in the endfgof saidpiston .rod'vremote froinf' saidvpiston, va carngonthejlowerend of said pedal leverrhaving a'portiomoperating against -raceof said; slot to 'drive-said piston in a compressive direction, `andaY loben-n said -carnwhichengages anotherface. of `saidslotto provide` a driving-,cminection for retracting' said piston to a fully 'retracted position at which positionsaid connection f is brokenc# 3. -In a `ilu-id pressureigsystem,.a pedal` leverf-, movableto and frQrn anat-xt estposition, a piston,-

a piston rod connecting said piston with said pedal lever, a slot adjacent the end of said piston rod, a pin slidable in said slot and fast on said pedal lever, a release member pivoted on said pin, said release member constituting a part of a one-Way driving connection for retracting said piston to its fullyvretracted position, means for latching said pedal lever and piston rod to one another at one end of the sliding motion of said pin in said slot, and means for releasing said latching means as the pedal approaches the'atrest position.

4. A iiuid pressure system, a reservoir, fluid in v said reservoir, a cylinder supportedin said reservoir in a horizontal position and surrounded by said fluid, a piston in said cylinder reciprocable from a fully retracted position to a fully extended position, means for reciprocating said piston including a pedal lever and a piston rod, a plurality of ports extending through the wall of said cylinder and having their principal axes located in the vsame vertical transverse plane of the cylinder, and spring means urging said piston to a position of rest in which said piston overlies and closes said ports, said piston-reciprocating means including a one-way releasable driving connection for retracting said piston to its fully retracted position to clear said ports, said connection being broken upon thev piston reaching its fully retracted position and including a pin and slot connection between the pedal lever and piston rod providing lost motion to permit spring means to urge the piston to the position of rest.

5. A fluid system, a pedal lever, a spring exerting rotating force against said pedal lever, a reservoir, fluid in said reservoir, a cylinder ysupported in said reservoir in a horizontal position and surrounded by said fluid, a, piston in said cylinder reci-procable from a fully retracted position to a fully extended position, means for reciprocating said piston, and means providing a one-way releasable lost-motion driving connection included in said piston-reciprocating means for retracting said piston to its fully retracted position, said one-way driving means cooperating with the pedal lever to break said driving connection with the piston upon its reaching its fully retracted position.

6. In a fluid pressure system, a cylinder, a pedal lever, a piston within said cylinder, a piston rod connecting said piston with the pedal lever through a one-way releasable lost-motion driving connection for reciprocating said-piston from a fully retracted to a fully extended position, said driving connection comprising a transverse slot in the end of said piston rod remote from said piston, a cam on the lower end'of said pedal lever having a portion operating against one face of said transverse slot to drive said piston in a compressive stroke, a lobe on said cam which engages another face of said slotgthereby making a driving connection retracting 'said piston to a fully retracted position, at which position said connection is broken, a vertical slot in said piston rod adjacent the end remote from said piston, and a pin slidable in said slot and fast on said pedal lever.

'7. In a uid pressure system, a pedal lever movable to and from an at-rest position, a reservoir, iluid in said reservoir, a cylinder supported in said reservoir and surrounded by said fluid, a piston in said cylinder reciprocable from a fully retracted position to a fully extended position, a piston rod, a one-way releasable lost-motion driving means connecting said piston rod repin, said release member having a driving surface arranged to cooperate with the driving suriace of the piston rod, said release member being biased about its pivotal connection with said lever to urge said driving surfaces into cooperating relationship, the length of the release member from the pin to the driving surface of the release member being equalA to the distance from the slot to the driving surface of the piston rod to permit the release member and piston to cooperate when the pin lies at one limit of its travel in said slot, said driving surfaces joining to make a driving connection as the movement of the pedal lever is reversed, and stop means on each of said pedal lever and said release member, said driving connection being broken by engagement of said stop means and rotation of said driving surfaces out of engagement with one another as said pedal lever returns toward fully retracted position.

8. In a fluid pressure system, a pedal lever, a reservoir, iluid in said reservoir, a cylinder supported in said reservoir and surrounded by said fluid, a piston in said cylinder reciprocable from a fully retracted position to a fully extended position, a piston rod, and means for reciprocating said piston and piston rod, said reciprocating means including a one-way releasable driving connection having a release mechanism cooperating with the movement of the pedal lever alternatively engaging said piston rod at the start of the retractile stroke and breaking said engagement when the full retractile position oi' the piston is reached.

9. In a fluid pressure system, a pedal lever, a spring exerting rotating force against said p-edal lever, a reservoir, iiuid in said reservoir, a cylinder supported in said reservoir and surrounded by said fluid, a piston in said cylinder reciprocable from a fully retracted position to a fully extended position, and means for reciprocating said piston, said reciprocating means comprising a piston rod connected at one end to said piston and connected at its other end to the pedal lever byv a one-way releasable lost-motion driving connection member, said connection member comprising a pin and slot arrangement between said pedal ylever and said driving connection member, and

means-rotatably mounted on said pin arranged to cooperate with the piston rod upon movement thereof, said means having a face designed to connect with a rearward face of said connection member, thereby forming a driving connection retracting said piston to a fully retracted position, at which position said connection is broken by the cooperation of said means with the pedal lever.

10. In a uid pressure system, a reservoir, fluid in said reservoir, a cylinder supported in said reservoir, a piston in said cylinder reciprocal from a fully retracted position to a fully extended position, means for reciprocating said piston including a pedal lever and a piston rod and a oneway releasable lost-motion driving connection therebetween designed for retracting said piston to fully retracted position and then reeasing said piston rod permitting movement of said piston in the opposite direction, and a compression spring extending between and seated on the closed retractile end of said cylinder and the retractile side of said piston urging said piston in the direction 11 :13 of its l.conzlpression stroke: taking up..the:llost motion of said driving connection.

11...In.auidpressure system, areservoinluid irzinlsaidreservoir, a cylinder supported in. said :'reservoirand surrounded bysaid fluid, a. piston ,in said cylinder reciprocable fromaiully retracted .position to a fully extended position, a L.pedal .'1ever,and a piston. rod attachedat one. end. to 7..:said-.pistonand yhaving a connectionmeansfor connectingsaid piston rodto said Apedal lever at y Yeits-...otliernend saidconnection means. comprising a memberwith a vertical slot to receive saidvpedal ,.,levenand a transverse slot to .slidably-receive a 4.pin.fast to saidpedal lever.

i 12...In a fluid pressure system, a reservoir, fluid Y ....insaidreservoir, a piston supported. in saidreseravoir; and .surrounded by .said-fluid. saidfpiston reciprocable from a. fully. retracted position to a .fully extended position, apiston rodsecured. to ....said.y piston, arotatableleyer, areleasable lostfmotion connection between the Aend of Said-piston ,.rodland -said lever. comprising a transverse .slot .-.in saidendocthe .piston rod, a. driving surface .onltherodfadjacent thesaid end othe 11oda.pin carriedadjacent the end oise-id levervzithinlsald slot,.and.rotatable meanscarried onsaidpin en- ,.gaging the drivngsurace.ofthercd atthe .bee1 lginning oi the movement fromthe fully extended positionl'of the piston. and disengaging said sur1 I face. at the fully retracted position of said-piston. ".13`...In a fluid pressure system, ,a reservoiniluid in said reservoir, av cylinder in said reservoir., a plurality of .ports extending from said reservoir through1 the Walls of said cylinder, atpiston'in said cylinder reciprocable from aully. retracted to v'a fullyexte'nded position, acompressionspring in '.said cylinder. abutting theiforward 'side Yof said Lpiston', a'pistonv rod. secured to.sald pistonv and Aextending outside said cylinder, a' rotatable lever, a lost-motion connection betweensaid levergand .1' the 'outer end of the piston rod'comprising a "transverse slot in the said endofthe rod, apin fcarried'within said slotby'the lever; a driving .surface'dened by theend of' said rod, a'driving means rotatable byxthelever Yandzcarried by `said pinjand adriving surface on said'driving L' meanstengaging said driving surface. of therod as the' rod is retractedand disengaging 'said'surface' at'the fully retracted position.

`14;"In afluid pressure system, a reservoir, id in said reservoir, apedal lever, a, cylinder in' 'said reservoir, a pistonin said cylinder, arod. con- 1 necting 'saidpiston' to said lever, a Aslot in` the endof' said rod remote from said piston, ai cam YTon theend of the lever adjacent said rodhaving a portion-engaging one face of said slotto drive said piston in' one direction, and a lobe onsaid cam ""Whichengages an opposite face'of said s1ot`to drivesaid piston in a retractile `direction to a'position' Where said lobe disengages. said ace.

15` In a fluid pressure system, a reservoir, fluid in' said reservoir, a pedal lever, a`V cylinder in said reservoir, a piston in said cylinder reciprocable from a fully retracted to a fully extended position; a rod secured to said piston, connectionV65 ineans'between the end of said rod remote fromV 12 s-.asaidpistomand they lower end of said levensomi .prising aslotinfsaiend' ofthe rod, a'pincarfried,bynsaidY lower end-fY of said'H lever :having a portion,-movable.'Within sadslot, means rotatable 5 by. saidflevenon said-pin, a lirstcarn surface :on 1..: saidend of..the.rod, and a-second cam surfaceon f said .means which; alternately: engages andv dis- A.engages-saidrst .cam surface.

.1., 16. .In anuidpressure system, a reservoir,.fluid wein saidf. reservoir, acylinder saidsreservoir, a ..splstonereclprocable;.from a ullyretracteclv to a fully extended position Within saidcylinder, a srod.;secured.to saidpiston, a-pedal lever, consnectionsmeans VjoiningsaidV lever tothe end .of 1;; i said-rod remote. from: said .piston comprising a :..xslotinfsaid.endofr saidfrod, a pin slidable Within said-slot vcarrledby-V said lever, aV rst cam surface con-salnrodfandmeans rotatable byv said lever and having a.camsurfacealternately engaging and..disengaging saidrst camsurface asy said Lpiston isfreciprocated from. .the fully extended .position totherfully. retracted position.

17..-In asuid. pressure system, a reservoir,.fluid ANY.ir1..-saidreservoir, a cylinder y.in'said reservoirin gg aehorizontalposition, a .pistoniin said cylinder reciprocable from aiullyretracted to a fully. bex- .-.tended.position, means for. reciprocating` said pis- ..ton, a.,port-communicating saidreservoir with ;-said cylinden. and means .urging saidpiston to a ,3Q wposition@- of-.rest .in whicnsaid. .piston` closes said ,s lportnsaid piston-reciprocating means including asone-.v,vay..releasable4 driving. connection. forv retractlng saiddpiston to itsfullyv retractedvposition ..t0..clearsald port,-.- said..connectio`n beingbroken ,ggeuponithepiston reachingits. fully retracted posivstion.

1.16....In afiuld.pressuresystem, a motion .trans- .initting means c comprising a.- fluid reservoir, a :cylindeninsaidreservoir, a pistonin said cylin- .yi .denreciprccable from aiullyretracted to a fully c extendedposition, a. port.communicating.said reservolnvvith said cylinder,.means..urging said .pistonto a positionof-rest.in which said piston .7. .closes.said.port,. and means for reciprocating said 4.3. vpiston including a .one-Way'. releasabledriving .connection for retracting saidpistonto clear said W-port,f said... connection. .being .broken after said piston has cleared said port.

- NILSERIK WAHLBERG.

'j-"REFERENCES vCITED 'Eheifcllowng :references L arel of record inthe file: offithisispatent z -IJNITED .STATES PJNJEQYJS .:':l\lumber Name 1 Date 1. :1,696,721 .Mattingly .De'c; 25, 1928 ;.11",85.1,226 iWhite Mar. 29, 1932 :.1,99.7100 l Boughton Apr. 9, 1935 -.\.12,054;862 Oliver ;fSept. 22, 1936 L: V2,076,363 'Brunner Apr. 6, 1937 -.2',16`0.,075 `La. Brie May 30, 1939 @2,232,350 Swift Feb. 18, 1941 ff2,340,466 t Gosling i Feb. 1, 1944 

